1. Field of the Invention
The present invention is related to a power regulator device, and more particularly a power regulator device that adjusts voltage of a power supplied to a load according to a pulse width modulation (hereinafter PWM) signal from an external digital control circuit.
2. Description of the Related Art
The resistor is connected to a power source of a load in serial so as to adjust the voltage of the power supplied to the load. However, the resistor consumes large power for the load. When a thyristor is developed, the thyristor is applied in a power circuit of the load to adjust the voltage of the power supplied to the load. Therefore, the power consumption is wildly decreased. At present, the thyristor is commonly applied in the power circuit of a fan, a heater, an elevator, or a crane etc. equipments.
With reference to FIG. 3, the heater (30) has a digital control circuit (31) for adjusting heating temperature, a power regulator unit (40) and a heating unit (32). Since a voltage of a power source of the digital control circuit (31) is smaller than that of the heating unit (32), the digital control circuit (31) is connected to the power circuit of the heating unit (32) through the power regulator unit (40). The power regulator unit (40) has a thyristor, and the thyristor is connected to the power source (33) of the heating unit (32) in serial. Therefore, when the digital control circuit (31) triggers different conduct angles of the thyristor, the voltage of the power supplied to the heating unit (32) is adjusted to increase or decrease.
In general, the power regulator unit (40) is an analog circuit, so the digital control circuit (31) has to output an analog signal to trigger the thyristor. Therefore, the heater (30) requires a digital to analog converter (DAC) (50) with high cost. The DAC (50) is connected between the digital control circuit (31) and the power regulator unit (40) and precisely converts the digital signal from digital control circuit (31) to the analog signal. The analog signal triggers the thyristor. Then, the digital control circuit (31) triggers the thyristor through the DAC (50).
With reference to FIG. 4, a functional diagram of another heater (30) is similar to the heater in FIG. 3, but the DAC (50) is directly designed in the digital control circuit (31a) so the control circuit (31a) outputs the analog signal to the power regulator unit (40). Therefore, the digital control circuit (31a) directly triggers the thyristor of the power regulator unit (40) to adjust the voltage of the power supplied to the heating unit (32).
Based on the foregoing description, the current equipments usually have the digital control circuits to control various functions of the equipments. The digital control circuit triggers the thyristor through the DAC. The cost of the digital control circuit will be increased.
To overcome the shortcomings, the present invention provides a PWM power regulator device to mitigate or obviate the aforementioned problems.